Rates of depression rise dramatically during adolescence (from 3-17%). Twice as many girls as boys will experience depression starting in early adolescence. Many individuals experience depression first during adolescence, and half of them may have a recurrence of depression later in adulthood. Thus, adolescence is a crucial time to study risk factors and mechanisms for developing depression, especially with girls, so that improved treatment/prevention programs may be created for this public health concern. This study aims to examine particular vulnerability factors and processes based on 3 different cognitive vulnerability- stress models of depression. Cognitive vulnerability to depression--the way in which individuals interpret negative information about the self and explain why negative events happen is an important risk factor that predicts the prospective development of depression. Cognitive vulnerability is actively operating by early adolescence, and negative life events increase throughout adolescence. Thus, the interaction of cognitive vulnerability with more negative events may be a potent explanation for the rise in depression observed during adolescence. This prospective study will test the hypothesis that the dramatic increase in depression during middle adolescence can be explained by a rising number of negative events interacting with higher levels of cognitive vulnerability. Also, cognitive vulnerability, negative events, and their interaction will be examined as an explanation for the emergence of the gender difference in depression among early adolescents. Last, the precise form of the cognitive vulnerability X stress interaction will be examined to see what combination of cognitive vulnerability and stress best predicts prospective changes in depression. Adolescents from 7th and 10th grade (200 in each grade for a total of 400; half girls) will be assessed initially and then at 4-month intervals for a total of 3 waves of data. The adolescents will be assessed for demographics, 3 forms of cognitive vulnerability, negative events, depressive symptoms, and pubertal status. Parents will provide collateral information on their children's symptoms and negative events. Multilevel growth curve analyses will be used to test the hypotheses.